Cod sursa(job #765758)
#include<iostream>
#include<fstream>
#include<vector>
#include<bitset>
using namespace std;
struct nod {
int y,m;
inline nod(int _y, int _m) {
y=_y;
m=_m;
}
};
struct stiva {
int x;
vector <nod> :: iterator it;
};
vector <nod> v[100001];
int gr[100001],s[500001];
bitset <500001> d;
stiva st[500001];
inline void dfs(int x)
{
int l,aux;
vector <nod> :: iterator it;
l=1;
st[1].x=x;
st[1].it=v[x].begin();
while(l>=1) {
aux=l;
for(it=st[l].it;it!=v[st[l].x].end();it++)
if(d[it->m]==0) {
d[it->m]=1;
s[l]=st[l].x;
st[l].it=it;
l++;
st[l].x=it->y;
st[l].it=v[it->y].begin();
break;
}
if(aux==l) {
l--;
if(l)
printf("%d ",s[l]);
}
}
}
#define DIM 30000
char buff[DIM];
int poz=0;
void citeste(int &numar)
{
numar=0;
while(buff[poz] <'0'||buff[poz]>'9')
if(++poz==DIM) {
fread(buff,1,DIM,stdin);
poz=0;
}
while('0'<=buff[poz]&&buff[poz]<='9') {
numar=numar*10+buff[poz]-48;
if(++poz==DIM) {
fread(buff,1,DIM,stdin);
poz=0;
}
}
}
int main ()
{
int n,m,i,x,y,c;
freopen("ciclueuler.in","r",stdin);
freopen("ciclueuler.out","w",stdout);
citeste(n);
citeste(m);
for(i=1;i<=m;i++) {
citeste(x);
citeste(y);
v[x].push_back(nod(y,i));
v[y].push_back(nod(x,i));
gr[x]++;
gr[y]++;
}
fclose(stdin);
c=1;
for(i=1;i<=n;i++)
if(gr[i]%2==1) {
c=0;
break;
}
if(c==0)
printf("-1");
else dfs(1);
fclose(stdout);
return 0;
}